Environmental Engineering Reference
In-Depth Information
the equator, and the northern hemisphere mass of
Laurussia
. Their
Hercynian
collision-
suture orogen is now widely dispersed, from the southern
Plate 11.1
The Atlantic Ocean clashes with the European
continent here, on the Pembroke coast of South Wales, in one
of Earth's most dynamic environments.
Photo: Ken Addison.
Appalachians, through southern Britain and north-central Europe to the Urals and north-
eastern Asia. Pangaea's Carboniferous-Permian-Triassic rocks reflect global palaeo-
climates with a major south-polar ice sheet, subtropical deserts and equatorial swamp
deltas and shallow, carbonate-rich seas (Figure 11.1). Rifting began in parts of Pangaea
just as other parts were sutured together,
c
. 255 Ma ago in the Permian period, as a
precursor of the eventual break-up. The early Mesozoic global Panthalassic Ocean
covered an entire hemisphere off Pangaea's west coast, with a major arm, the Tethys
Ocean, partially enclosed by its more indented east coast. Sea-floor spreading opened
new oceans at their expense.
American plates moved west as the Atlantic opened, consuming the
Panthalassic/Pacific Ocean faster than it was spreading. Their respective ocean basin
areas have changed by +160 per cent and −35 per cent during the Cenozoic (Figure 11.2).
Cordilleran systems on the American Pacific coasts have incorporated older, Palaeozoic
subduction terranes and North America has now overrun much of the Pacific mid-ocean
ridge. The Panthalassic and Tethys Oceans were also under attack from the eastward
fragmentation of Gondwanaland and its
